Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

806
FXUS63 KLOT 101444
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
944 AM CDT Tue Mar 10 2026

.KEY MESSAGES...

- Areas of dense fog this morning, mainly near/north of I-80.

- Severe thunderstorms this afternoon and evening, with the
  potential for very large hail, damaging winds and tornadoes.

- Potential for heavy rain and localized flash flooding this
  afternoon into Wednesday morning.

- Small potential for damaging winds continuing into Wednesday
  morning across our far south and east.

- Possible very strong winds (45+ mph) Thursday night/Friday.

&&

.UPDATE...
Issued at 945 AM CDT Tue Mar 10 2026

Mid-morning surface analysis depicts a frontal boundary ever so
gradually inching south between the I-80 and I-88 corridors. A
narrow corridor of dense fog can be found near I-88 and I-90,
mainly west of the interior metro area near and north of the
front. Cool northerly flow behind the front have dropped
temperatures in our north into the 40s, even upper 30s near the
lakeshore in Lake and Cook counties. Meanwhile, efficient warm,
moist advection is taking place south of the front with
temperatures and dewpoints both in the upper 50s to around 60
degrees. The clashing of these two air masses will continue to
sharpen up this boundary considerably for the afternoon and
evening. By early afternoon, the front is expected to be hung up
somewhere near I-80, and perhaps a bit south of I-80 closer to
mid- afternoon.

Two upstream waves are in the process of phasing along this
baroclinic zone, one ejecting northeast out of the southern
Plains and another pushing off the lee of the High Plains. The
resulting surface low is spinning up over Kansas and will
propagate northeastward into Iowa this afternoon. East of this
feature, an expansive EML is overspreading the region; the 12Z
ILX RAOB depicts ~7.5 K/km lapse rates through the mid levels.
We`ll see an uptick in dynamic forcing ahead of this wave
overspread the region into the afternoon.

A southwesterly mid level impulse is progged to strengthen on
the eastern flank of the low and nose into western and northern
IL early this afternoon. Guidance remains unsure as to whether
convective initiation (CI) will occur with this feature, but
this will be our first chance at severe convection today. Last
night, CAM guidance had been largely backing off on storms
developing with this wave. However, some of them, including the
HRRR, are back on this signal while the regional/global camps
have been more steadfast in storms developing. The HRRR has also
been trending earlier into the afternoon with CI associated
with this feature. This morning`s 12z run has storms going up
southeast of the Quad Cities and into the IL River valley
outside of the CWA by 19Z, and tracking a cluster of supercells
into our area in the early- mid afternoon, focusing near and
south of the front.

Unfortunately, model variability in this time window remains
too high for our liking at this range. A very, very close eye
will need to be kept on upstream conditions heading into early
afternoon. If CI were to take place during this time, supercell
environments are progged featuring 1,000 to 2,000 J/kg of
largely uncapped CAPE south of the front and long, curved low
level hodographs. All hazards will be possible near and south of
the front, including tornadoes. Any storms that push north of
the front should quickly become elevated, but could feature
torrential downpours and possibly large hail with considerable
mid level shear, RH, and instability.

Even better parameter spacing is expected mid-afternoon into
this evening. An expansive SSW LLJ will strengthen considerably
across IL and nose into northern IL during the latter half of
today. This will bring a notable uptick in moist upglide and
large scale forcing around the area. South of the front, it
should also add further curvature to low level hodographs and
drive up MLCAPE values, including through the lowest 100 mb,
which will drive up the strong tornado potential. As a result,
convection is anticipated to blossom over the area during this
time with the highest coverage of storms expected near and south
of the front.

This is a long-winded way of saying that the going forecast is
very much on track, but not much has become any clearer since
last night`s package. Keep an eye on the weather in the area
beginning in the early afternoon. For any further details, refer
to the full discussion below.

Doom

&&

.DISCUSSION...
Issued at 218 AM CDT Tue Mar 10 2026

Through Wednesday:

Moisture is surging northward early this morning, with
dewpoints pushing into the upper 50s and lower 60s across the
region. Pockets of low stratus and shallow mist have recently
developed, and this will likely continue to expand north of I-80
and the Illinois river through daybreak. Surface flow is
forecast to remain elevated, but given the recent expansion of
sub 1/2 mile visibilities, may need to shortly consider a dense
fog advisory for parts of the area.

Somewhat of a complex severe weather setup is evident later
this afternoon and overnight with quite a few moving parts and
generally nebulous/subtle large scale forcing mechanisms. As a
result, uncertainty in the precise evolution of thunderstorms
remains, but the ceiling on the severe weather potential in the
region is anomalously high for this time of year.

The first key player is an extremely shallow cold front that`s
presently rolling down the lake and into southern Wisconsin.
This front is so shallow that it`s not super evident even on the
MKX radar, which certainly corroborates forecast soundings from
the NAM/NAMNest which depict the frontal inversion sitting
around 700 feet. These types of shallow early-spring boundaries,
enhanced by the cold Lake Michigan waters, often have an
impressive ability to plow southward and undercut even deep
moist boundary layers. This backdoor front will likely be no
exception, with the latest guidance suggesting this will surge
south to near a Rockford - St. Charles - Crown Point, IN line by
midday before settling in the vicinity of to just south of the
I-80 corridor by mid afternoon before becoming quasistationary.
Behind the front, temperatures will fall to either side of 40 at
the lake front and into the 40s/maybe low 50s inland as low
stratus expands atop the frontal inversion (perhaps with some
scattering in the afternoon, mainly along the southern flanks).

While low stratus may develop south of I-80 through this
morning, forecast soundings indicate this would be quite thin
and likely to mix out readily. As a result, temperatures are
expected to surge through the 70s, if not tagging 80 on a
localized basis towards central Illinois this afternoon. As
dewpoints surge into the mid and upper 60s, an expansive
elevated mixed layer characterized by 500-700 mb lapse rates of
7.5 to 8.5 C/km will overspread the region leading to a rapid
increase in conditional instability with MLCAPE values progged
to rise through 2000-3000 J/kg during the afternoon.

Given the relatively warm base to the EML, things look to remain
decidedly capped to surface-based convection through at least
early afternoon in the region until additional modest ascent
approaches the region. Key player number 2 appears to be a
mid-level perturbation that`s currently pushing out of the
Texas/Oklahoma Panhandles and into Kansas. While global
guidance has been fairly steady with this feature, have noted
some more significant variability with the CAMs which in turn
seems to be playing a role in the run-to-run variability in
convective initiation (or not) by early-mid afternoon near and
southeast of the Quad Cities as the associated DCVA with this
feature is not particularly robust, and the main jet core may
only provide a glancing blow across the sharpening
quasistationary/warm frontal zone before continuing
northeastward. Whether explosive CI occurs in the vicinity of a
Moline to Ottawa line in the roughly 2 - 4 PM timeframe remains
a key detail to iron out. If CI occurs here, this would be very
concerning as semi-discrete supercellular convection would be
favored within a strongly sheared environment supportive of all
severe hazards including tornadoes, very large hail, and
damaging winds.

While recent runs of the HRRR have mostly lost this convection, the
fact that the globals (GFS, ECMWF, UKMET) have been fairly
steadfast in convective development in this zone remains
concerning. Have continued to paint generally chance PoPs in
this corridor during the afternoon, and we`ll need to carefully
monitor this zone. *IF* semi-discrete cells can develop and
sustain in this corridor south of the front, there would
certainly be a threat for strong tornadoes.

Isentropic upglide atop the sharp frontal inversion and
generally increasing large scale forcing as the main surface low
approaches will eventually lead to an expansion of thunderstorms
through Tuesday evening. Surface based convection south of the
front will continue to pose an all-hazards severe threat deep
into the evening. While a tornado threat can occasionally occur
many miles north of warm fronts, this appears unlikely in this
scenario given the sharp nature of this feature. As a result,
any storms that track northeast and atop the frontal zone will
quickly become elevated. Additional convection will likely
develop through the evening across northern Illinois in response
to intensifying upglide. Storms north of I-80 will pose a threat
for large--possibly very large--hail as forecast soundings
reveal strong inflow-layer storm-relative winds and significant
1-7 km shear. If very robust supercells can sustain themselves,
isolated damaging wind gusts may still materialize north of the
front as well.

Regarding the flood potential: the generally southwesterly
500-mb flow does not exactly match some of the more significant
Maddox type flash flood setups in the region. That said,
corridors of southwest to northeast oriented thunderstorms will
pose a threat for at least localized training and very heavy
rainfall. Some increased concern for flooding exists for areas
like Chicago and parts of the south and southeast burbs where
heavy rain fell a few days ago. Will refresh the Hydrologic
Outlook. Can`t rule out needing a targeted flash flood watch
down the line if corridors of heavier training convection can be
nailed down a bit better.

The threat for strong-severe storms will possibly continue
through the night. Noting another early window Wednesday
morning as a possibly convectively-augmented MCV and vort lobe
tracks across our southeast around or just after daybreak.
Guidance suggests that surface-based convection would still be
possible during this period south and east of a Pontiac to
Rensselaer line, with a threat for damaging wind gusts and
perhaps some embedded QLCS tornado threat. This is somewhat
lower confidence at this time, but something we`ll need to keep
an eye on.

Fairly widespread showers will then occur through the balance of
Wednesday as a cold front eventually works its way through the
area. Some potential for precip to turn over to a little snow
across far northern Illinois, but temperatures look to remain
largely at or above freezing. Could even be a potential for a
little drizzle as things come to an end, but again not concerned
about wintry impacts at this point due to forecasted
temperatures. Have boosted wind gusts Wednesday afternoon as
steepening boundary layer lapse rates should result in at least
periodic 30-40 mph gusts.

Carlaw


Wednesday night through Monday:

It looks like we`ll get a bit of a break Wednesday night into
Thursday as high pressure shifts off to our south. Noting some
potential for fairly deep mixing Thursday afternoon and for RH
values to fall around or under 30 percent with breezy westerly
winds. Given the rain forecast over the next 24 hours, this
doesn`t currently look like an elevated fire threat.

Thursday night into Friday, a robust surface low (mid 980s mb)
is forecast to track to our north, roughly across the Door
Peninsula and across northern lower Michigan. Noting a huge low-
level mass response in the guidance, with 850 mb winds near 70
knots advertised across the guidance suite. While some low cloud
cover and at least spotty light precipitation (rain) will be
possible, deeper-than-typical mixing during the late overnight
hours into Friday morning may yield a significant increase in
winds and gusts. Concerningly, latest GFS soundings show roughly
50 knot boundary layer mean winds during this time frame, with
even steeper lapse rates developing after daybreak Friday in the
cold advection regime. Have increased winds and gusts a bit
with this forecast package above the NBM-delivered values, but
suspect things remain notably underdone at this time. At this
time, can`t rule out high wind warning type winds and gusts into
Friday morning given the latest model trends.

Winds will ease sharply Friday evening as high pressure again
builds across the region. There may be some additional precip
chances towards the Saturday night - Sunday morning timeframe
as mid-level frontogenesis intensifies in advance of the next
disturbance, although the latest guidance suggests most of this
activity may end up shifting largely north of the region.
Thereafter, global deterministic and ensemble guidance suggest
the potential for yet another robust surface low spinning up in
the general vicinity on Sunday and into Sunday night. A much
colder airmass bottled up to the north looks like it`ll get
dislodged with this feature and surge across our area during
this timeframe. While model variability remains somewhat high at
this juncture, can`t totally rule out old man winter making
another return to the region with some snow potential into early
Monday morning.

Carlaw

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 642 AM CDT Tue Mar 10 2026

Primary forecast concerns include...

Wind shift to northeast this morning.
Ifr/lifr cigs this morning and again tonight.
Scattered strong/severe thunderstorms this afternoon/evening.
Dense fog with lifr/vlifr vis at times.

The cold front is slowly working its way down the northeast IL
shore of Lake Michigan and will move across the Chicago
terminals over the next few hours, shifting winds to the north/
northeast. Directions will turn northeast later this morning and
more easterly this afternoon. Speeds in the 10-12kt range are
expected with higher gusts at times. A warm front will lift
northeast this evening and may allow winds to briefly turn back
southerly at MDW/GYY but confidence is low. Winds will turn to
the north/northwest overnight.

Areas of dense fog continue across parts of northwest IL and at
RFD and this fog is expected to slowly lift this morning.
Additional fog may move inland from Lake Michigan today and
also tonight, but confidence is low. If this fog were develop
inland, it may also become dense.

Ifr and possibly lifr cigs are expected to move back across the
Chicago terminals behind the cold front noted above. These cigs
are then still expected to lift back to low mvfr this afternoon.
Cigs may tank back into lifr or vlifr this evening and if they
do, they may persist through daybreak Wednesday morning, before
slowly lifting later Wednesday morning.

Scattered thunderstorms are expected to develop during the mid
to late afternoon and likely right over, or just southwest of
the terminals. Confidence for exact location remains medium and
maintained prob mention for now, but tempo mention may be needed
with later forecasts. The highest coverage of thunderstorms may
still be during the early/mid evening which the current tempo
handles well. The thunderstorm activity is expected to be moving
east and southeast of the terminals by 06z. Scattered showers
are expected to continue overnight into Wednesday morning. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Dense Fog Advisory until 11 AM CDT this morning for ILZ003-
     ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-ILZ012.

IN...None.
LM...Small Craft Advisory until 4 AM CDT Thursday for Winthrop
     Harbor to Northerly Is. IL.

     Small Craft Advisory from 10 AM Wednesday to 4 AM CDT Thursday
     for Northerly Is. to Gary IN.

     Small Craft Advisory from 10 AM Wednesday to 10 AM CDT
     Thursday for Gary to Burns Harbor IN-Burns Harbor to
     Michigan City IN.

&&

$$

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